1. Field
The present disclosure relates to a thermoelectric material having a high performance index, thermoelectric modules including the thermoelectric material, and thermoelectric devices including the thermoelectric modules, and more particularly, to a thermoelectric material having a large Seebeck coefficient, a high electrical conductivity, and a low thermal conductivity, thermoelectric modules including the thermoelectric material, and thermoelectric devices including the thermoelectric modules.
2. Description of the Related Art
In general, thermoelectric materials are used in active cooling and waste heat power generation based on the Peltier effect and the Seebeck effect. The Peltier effect is a phenomenon in which, as illustrated in FIG. 1, holes of a p-type material and electrons of an n-type material move when a DC voltage is applied to the materials, and thus exothermic and endothermic reactions occur at opposite ends of each of the n-type and p-type materials. The Seebeck effect is a phenomenon in which, as illustrated in FIG. 2, holes and electrons move when heat is provided by an external heat source and thus electric current flows in a material, thereby converting a temperature difference into electrical power.
Active cooling using a thermoelectric material improves the thermal stability of a device, does not produce vibration and noise, and use of a separate condenser and refrigerant may be avoided; thus thermoelectric cooling is regarded as an environmentally friendly method of cooling. Active cooling using a thermoelectric material can be applied in refrigerant-free refrigerators, air conditioners, and various micro-cooling systems. In particular, if a thermoelectric device is attached to a memory device, the temperature of the memory device may be maintained at a uniform and stable level while an increase in the entire volume of the memory device and the cooling system is smaller than if a commercially available adiabatic cooling system is used. Thus, use of thermoelectric devices in memory devices may contribute to higher performance.
In addition, when thermoelectric materials are used for thermoelectric power generation based on the Seebeck effect, waste heat may be used as an energy source. Thus the energy efficiency of a vehicle engine, an exhaust device, a waste incinerator, a steel mill, or a medical device power source which uses heat from a human body may be increased, or the waste heat can be collected for use in other applications.
The performance of a thermoelectric material is evaluated using a dimensionless performance index (“ZT”) defined by Equation 1.
                    ZT        =                                            S              2                        ⁢            σ            ⁢                                                  ⁢            T                    k                                    Equation        ⁢                                  ⁢        1            In Equation 1, S is a Seebeck coefficient, a is an electrical conductivity, T is an absolute temperature, and κ is a thermal conductivity.
To increase the ZT, a material having a large Seebeck coefficient, a high electrical conductivity, and a low thermal conductivity would be desirable.